How Can I Make My App Remeber/save The Coins My App Users Earned My App?

I want my app to remember or save the number of coins that users earn in my app so that whenever they open my app again they can see their coins instead of a 0.

Solution 1:

You should use shared preferences on Android.

I write down a fully functional example of an application of a shared preferences. This one is taken from my project (link down the code).

First, you should create a class (supposing that your "coins" will be used in more activities). This one is called SessionManager.java:

publicclassSessionManager {
    // Shared Preferences
    SharedPreferences pref;

    // Editor for Shared preferences
    Editor editor;

    // Context
    Context _context;

    // Shared pref modeintPRIVATE_MODE=0;

    // Sharedpref file nameprivatestaticfinalStringPREF_NAME="FoodAdvisorPref";

    // All Shared Preferences KeysprivatestaticfinalStringIS_LOGIN="IsLoggedIn";
    publicstaticfinalStringKEY_AZIENDA="aziendaName";
    publicstaticfinalStringKEY_EMAIL="email";
    publicstaticfinalStringKEY_NAME="name";
    publicstaticfinalStringKEY_SECOND_NAME="second_name";
    publicstaticfinalStringKEY_DESCRIPTION="description";
    publicstaticfinalStringKEY_ID="id";
    publicstaticfinalStringKEY_PHOTO="photo";



    // ConstructorpublicSessionManager(Context context){
        this._context = context;
        pref = _context.getSharedPreferences(PREF_NAME, PRIVATE_MODE);
        editor = pref.edit();
    }


    /**
     * Create login session
     * */publicvoidcreateLoginSession(String azienda,String name,String second_name, String email,String description,String id,String photo){
        // Storing login value as TRUE
        editor.putBoolean(IS_LOGIN, true);

        editor.putString(KEY_NAME, name);
        editor.putString(KEY_EMAIL, email);
        editor.putString(KEY_AZIENDA,azienda);
        editor.putString(KEY_SECOND_NAME,second_name);
        editor.putString(KEY_DESCRIPTION,description);
        editor.putString(KEY_PHOTO,photo);
        editor.putString(KEY_ID,id);
        // commit changes
        editor.commit();
    }

    /**
     * Check login method wil check user login status
     * If false it will redirect user to login page
     * Else won't do anything
     * */publicvoidcheckLogin(){
        // Check login statusif(!this.isLoggedIn()){
            // user is not logged in redirect him to Login ActivityIntenti=newIntent(_context, LoginActivity.class);
            // Closing all the Activities
            i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

            // Add new Flag to start new Activity
            i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

            // Staring Login Activity
            _context.startActivity(i);
        }

    }


//session data like hashpublic HashMap<String, String> getUserDetails(){
        HashMap<String, String> user = newHashMap<String, String>();
        user.put(KEY_NAME, pref.getString(KEY_NAME, null));
        user.put(KEY_EMAIL, pref.getString(KEY_EMAIL, null));
        user.put(KEY_AZIENDA, pref.getString(KEY_AZIENDA, null));
        user.put(KEY_SECOND_NAME, pref.getString(KEY_SECOND_NAME, null));
        user.put(KEY_DESCRIPTION, pref.getString(KEY_DESCRIPTION, null));
        user.put(KEY_ID, pref.getString(KEY_ID, null));
        user.put(KEY_PHOTO,pref.getString(KEY_PHOTO,null));

        return user;
    }

//close sessionpublicvoidlogoutUser(){
        // Clearing all data from Shared Preferences
        editor.clear();
        editor.commit();

        // After logout redirect user to Loing ActivityIntenti=newIntent(_context, LoginActivity.class);
        // Closing all the Activities
        i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

        // Add new Flag to start new Activity
        i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

        // Starting Login Activity
        _context.startActivity(i);
    }

    // Get Login StatepublicbooleanisLoggedIn(){
        return pref.getBoolean(IS_LOGIN, false);
    }
}

To use this class in the others activities:

SessionManager session; //as global variable if you want
  session = new pro.rane.foodadvisor.SessionManager(getApplicationContext()); //inside create view
 session.checkLogin();
 // get user data from sessionHashMap<String, String> user = session.getUserDetails();
 // name exampleString name = user.get(SessionManager.KEY_NAME);
 // email exampleString email = user.get(SessionManager.KEY_EMAIL);

Here is the source of my project.

Here is a practical link by tutorials point.

Here is the official guide for Android developers.

Solution 2:

There're different ways to store data on Android. Read this guide and decide which one is more suitable for you task.

Solution 3:

Use the Java Preferences API.

import java.util.prefs.*;

publicclassExample {
// Preference keyprivatestaticfinalStringCOIN="coin";

publicvoidsavePreference(String coinValue) {
    Preferencesprefs= Preferences.userNodeForPackage(Example.class);

    prefs.put(Coin, coinValue);
}

public String readPreference() {
    Preferencesprefs= Preferences.userNodeForPackage(Example.class);

    return prefs.get(COIN, "default");
}
}

The data is stored based on the fully-qualified name of your class, so your package name and class name are relevant. From the documentation for the Preferences class:

This class allows applications to store and retrieve user and system preference and configuration data. This data is stored persistently in an implementation-dependent backing store. Typical implementations include flat files, OS-specific registries, directory servers and SQL databases. The user of this class needn't be concerned with details of the backing store.